TY - JOUR
T1 - Heterodimeric amino acid transporter glycoprotein domains determining functional subunit association
AU - Franca, Raffaella
AU - Veljkovic, Emilija
AU - Walter, Stefan
AU - Wagner, Carsten A.
AU - Verrey, François
PY - 2005/6/1
Y1 - 2005/6/1
N2 - The heteromeric amino acid transporter glycoprotein subunits rBAT and 4F2hc (heavy chains) form, with different catalytic subunits (light chains), functional heterodimers that are covalently stabilized by a disulphide bridge. Whereas rBAT associates with b0,+ AT to form the cystine and cationic amino acid transporter defective in cystinuria, 4F2hc associates with other homologous light chains, for instance with LAT1 to form a system L neutral amino acid transporter. To identify within the heavy chains the domain(s) involved in recognition of and functional interaction with partner light chains, chimaeric and truncated forms of rBAT and 4F2hc were co-expressed in Xenopus laevis oocytes with b0,+ AT or LAT1. Heavy chain-light chain association was analysed by co-immunoprecipitation, and transport function was tested by tracer uptake experiments. The results indicate that the cytoplasmic tail and transmembrane domain of rBAT together play a dominant role in selective functional interaction with b0,+ AT, whereas the extracellular domain of rBAT appears to facilitate specifically L-cystine uptake. For 4F2hc, functional interaction with LAT1 was mediated by the N-terminal part, comprising cytoplasmic tail, transmembrane segment and neck, even in the absence of the extracellular domain. Alternatively, functional association with LAT1 was also supported by the extracellular part of 4F2hc comprising neck and glycosidase-like domain linked to the complementary part of rBAT. In conclusion, the cytoplasmic tail and the transmembrane segment together play a determinant role for the functional interaction of rBAT with b0,+ AT, whereas either cytoplasmic or extracellular glycosidase-like domains are dispensable for the functional interaction of 4F2hc with LAT1.
AB - The heteromeric amino acid transporter glycoprotein subunits rBAT and 4F2hc (heavy chains) form, with different catalytic subunits (light chains), functional heterodimers that are covalently stabilized by a disulphide bridge. Whereas rBAT associates with b0,+ AT to form the cystine and cationic amino acid transporter defective in cystinuria, 4F2hc associates with other homologous light chains, for instance with LAT1 to form a system L neutral amino acid transporter. To identify within the heavy chains the domain(s) involved in recognition of and functional interaction with partner light chains, chimaeric and truncated forms of rBAT and 4F2hc were co-expressed in Xenopus laevis oocytes with b0,+ AT or LAT1. Heavy chain-light chain association was analysed by co-immunoprecipitation, and transport function was tested by tracer uptake experiments. The results indicate that the cytoplasmic tail and transmembrane domain of rBAT together play a dominant role in selective functional interaction with b0,+ AT, whereas the extracellular domain of rBAT appears to facilitate specifically L-cystine uptake. For 4F2hc, functional interaction with LAT1 was mediated by the N-terminal part, comprising cytoplasmic tail, transmembrane segment and neck, even in the absence of the extracellular domain. Alternatively, functional association with LAT1 was also supported by the extracellular part of 4F2hc comprising neck and glycosidase-like domain linked to the complementary part of rBAT. In conclusion, the cytoplasmic tail and the transmembrane segment together play a determinant role for the functional interaction of rBAT with b0,+ AT, whereas either cytoplasmic or extracellular glycosidase-like domains are dispensable for the functional interaction of 4F2hc with LAT1.
KW - Amino acid influx
KW - Amino acid transporter
KW - Coimmunoprecipitation
KW - Glycoprotein
KW - Subunit association
KW - Xenopus laevis oocyte
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U2 - 10.1042/BJ20050021
DO - 10.1042/BJ20050021
M3 - Article
C2 - 15679469
AN - SCOPUS:20544449944
VL - 388
SP - 435
EP - 443
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
IS - 2
ER -